Method and apparatus for performing three-dimensional measurement

• US 20090066968A1
• Filed: 08/28/2008
• Published: 03/12/2009
• Est. Priority Date: 08/29/2007
• Status: Active Grant

• Current Assignee: Omron Corporation
• Original Assignee: Omron Corporation
• Inventors: Ikeda, Yasuyuki, Yano, Hiroshi, Fujieda, Shiro
• Granted Patent: US 8,648,895 B2
• Time in Patent Office: Days
• US Class Current: 356/602
• CPC Class Codes: G01B 11/03 by measuring coordinates of points
• CPC Class Codes: G01B 11/245 using a plurality of fixed, simultaneously operating transducers G01B11/2408 - G01B11/2425, G01B11/255 take precedence

Abstract

A control processing unit simultaneously drives cameras to produce images of a measuring object, the control processing unit searches corresponding point on a comparative image produced by one of the cameras for a representative point in a reference image produced by the other camera, and the control processing unit computes a three-dimensional coordinate corresponding to a coordinate using the coordinate of each point correlated by the search. The control processing unit also obtains a shift amount at the corresponding point specified by the search to an epipolar line specified based on a coordinate of a representative point on the reference image side or a parameter indicating a relationship between the cameras, and the control processing unit supplies the shift amount as an evaluation value indicating accuracy of three-dimensional measurement along with three-dimensional measurement result.

Claims

1. A three-dimensional measurement method in which a plurality of cameras are disposed while a positional relationship and optical axis directions are fixed such that visual fields of the cameras overlap within a predetermined range, particular one camera of the plurality of cameras is set at a reference camera, and three-dimensional measurement is performed to a measuring object by performing a first step, a second step, a third step, and a fourth step predetermined times, the measuring object entering a range where visual fields of the plurality of cameras overlap being taken by the cameras in the first step, a representative point of the measuring object being extracted from a reference image produced by the reference camera in the second step, a point corresponding to the representative point on the reference image side being searched in an image produced by a camera except for the reference camera in the third step, a three-dimensional coordinate corresponding to a coordinate being obtained using the coordinate of each point correlated by the search of the third step in the fourth step,

wherein, when three-dimensional measurement processing is performed to one measuring object, a shift amount at the corresponding point obtained by the search of the third step to an epipolar line based on a predetermined relationship between the camera and the coordinate of the representative point in the reference image is computed for at least one representative point, evaluation information indicating accuracy of three-dimensional measurement result is set based on the computed shift amount, and the evaluation information is supplied along with the three-dimensional measurement result of the measuring object.

2. The three-dimensional measurement method according to claim 1, wherein not less than three cameras are used, the cameras expect for the reference camera are individually combined with the reference camera, the second, third, and fourth steps and the shift amount computation processing are performed in each combination, and the evaluation information is supplied based on the largest shift amount.

3. A three-dimensional measurement apparatus comprising:

an image input unit into which an image of a measuring object entering a range where visual fields of a plurality of cameras overlap is individually fed from the plurality of cameras, the plurality of cameras being disposed while a positional relationship and optical axis directions are fixed such that the visual fields of the cameras overlap within a predetermined range;

a representative point extraction unit which extracts a representative point of the measuring object from a reference image produced by a reference camera while particular one camera of the plurality of cameras is set at the reference camera;

a corresponding point search unit which searches a point corresponding to the representative point on the reference image side in an image produced by a camera except for the reference camera;

a three-dimensional coordinate computation unit which obtains a three-dimensional coordinate corresponding to a coordinate using the coordinate of each point correlated by the search processing of the corresponding point search unit; and

an output unit which supplies three-dimensional measurement result information based on the three-dimensional coordinates computed for predetermined representative points extracted by the representative point extraction unit,

wherein the three-dimensional measurement apparatus further comprises a shift amount computation unit which computes a shift amount at the corresponding point obtained by the search of the corresponding point search unit to an epipolar line based on a predetermined relationship between the camera and the coordinate of the representative point in the reference image is computed for at least one representative point when three-dimensional measurement processing is performed to one measuring object, and

the output unit sets evaluation information indicating accuracy of three-dimensional measurement result based on the shift amount computed by the shift amount computation unit and supplies the evaluation information along with the three-dimensional measurement result of the measuring object.

4. The three-dimensional measurement apparatus according to claim 3, wherein images are fed into the image input unit from not less than three cameras,

in the corresponding point search unit, the three-dimensional coordinate computation unit, and the shift amount computation unit, the cameras except for the reference camera are individually combined with the reference camera, and processing is performed in each combination, and

the output unit produces and supplies the evaluation information based on a maximum value of the shift amounts computed in the combinations of the cameras.

5. The three-dimensional measurement apparatus according to claim 3, further comprising a notification unit which makes a notification for warning, when the shift amount used to produce the evaluation information exceeds a predetermined permissible value, or when a degree of reliability of the three-dimensional measurement result indicated by the evaluation information is lower than a predetermined reference value.